P2457

Diesel Particulate Filter Differential Pressure Sensor Circuit High

Indicator

The PCM has detected an abnormal voltage reading (high or low) from the diesel particulate filter pressure sensor circuit. Diesel particulate filter pressure is monitored exclusively in vehicles equipped with diesel engines. "Sensor A" indicates a particular sensor. Consult the manufacturer's service manual (or equivalent) for the location of this particular sensor.

Code Set Parameters

Diesel particulate filter pressure is monitored by the diesel particulate filter pressure sensor. The 5-volt (maximum) variable resistance circuit supplies input voltage to the PCM. The PCM calculates the desired diesel particulate filter pressure using input data from the throttle position sensor, mass air flow sensor, tachometer, etc. Actual diesel particulate filter pressure is then compared with desired diesel particulate filter pressure. Variations that exceed the manufacturer's recommended diesel particulate filter pressure will result in a stored trouble code and an illuminated service engine soon lamp. If the diesel particulate filter sensor circuit voltage falls below .022 psi at idle (consult the manufacturer's service manual for the specs on your particular application) a code will be stored and a service engine soon lamp will be illuminated. If the diesel particulate filter pressure sensor signal value at part load is less than a minimum value (or greater than a maximum value) when the engine is running a code will be stored and a service engine soon lamp will be illuminated. Minimum and maximum reference values are based on overall exhaust volume.

Symptoms

If this code is stored in the PCM, the malfunction indicator lamp should be illuminated. Chances are that there will be no other symptoms associated with this type of code other than the possibility of other related trouble codes.

Common Causes

In most cases, this code is caused by a clogged diesel particulate filter or defective diesel particulate filter pressure sensor. However, technicians also report that damaged and burnt electrical wiring and connectors are a possibility. Other causes may include a cracked, loose, or disconnected hose to the diesel particulate filter pressure sensor. The PCM could also be faulty but this is highly unlikely.

Common Misdiagnosis

The diesel particulate pressure sensor is frequently replaced in error when a clogged or restricted filter is the culprit.

Diagnosis

The diesel exhaust after treatment system consists of an underhood pre-catalyst and an underbody catalyst

The underbody catalytic converter also consists of the main diesel oxidation catalyst and the coated diesel particulate filter

The main function of the diesel particulate filter is to collect particulates from the engine exhaust in order to minimize the discharge of pollutants in the atmosphere

Pollutants (seen as soot particles) accumulate in the channels of the DPF and are burned off at regular intervals through a process called regeneration

Excessive accumulation of pollutants in the diesel particulate filter can cause a drop in engine performance

During regeneration, additional fuel is injected via multiple post injections in order to increase the exhaust gas temperature

The diesel particulate filter temperature is increased to approximately 1,110°F during this process and the accumulated pollutants are oxidized or burned off into carbon dioxide.
The diesel particulate filter pressure system uses a variable capacitance sensor to monitor diesel particulate filter pressure and input data to the PCM

The PCM calculates the desired amount of diesel particulate filter pressure by considering inputs from various other engine and drivability sensors

Always retest the system after repairs are completed to ensure success.
If all system wiring, connectors, and components (Including fuses) appear to be in normal working order, connect the scanner (or code reader) to the diagnostic connector and record all stored codes and freeze frame data

This information can be extremely helpful in diagnosing intermittent conditions that may have contributed to this code being stored

Continue by clearing the code and operating the vehicle to see if it returns

This will help to determine whether or not the malfunction is intermittent

After the codes are cleared, test drive the vehicle to see if the code returns

If the code fails to immediately return, you may have an intermittent condition

Intermittent conditions can prove to be quite a challenge to diagnose and in extreme cases may have to be allowed to worsen before a correct diagnosis can be made

Repair open or shorted wiring, components, or connectors as required.
If the electrical circuits and the exhaust back pressure vent control solenoid comply with the manufacturer's specifications, suspect a defective PCM

Keep in mind that PCM failure is rare and replacement will require reprogramming.